1. Field of Invention
The present invention relates to an affixing device. More particularly, the present invention relates to an affixing device used for affixing a front cover, a back cover, and a battery unit of a personal digital assistant (PDA).
2. Description of Related Art
As the high technology industry is greatly and rapidly developed, the technology is updated day by day. So many versatile electronic products have been developed. In the recent years, the functions of the portable products have been greatly improved, with increasingly diverse abilities. As a result, it can provide convenience for the user in managing the daily routine work or the personal business in a quite flexible way without being limited by the office location and the office hour. In particular, the product of the personal digital assistant (PDA) has been introduced to the market, and brings the user many conveniences. However, since the PDA uses a battery for supplying the needed power, the powering period is limited. Some manufactures would add an extra battery on the back surface of the housing of the personal digital assistant, so as to prolong the PDA's usage time period. The conventional method of how to affix the extra battery unit to the housing of the PDA is described in the following.
Referring to FIG. 1, it is an exploded drawing, schematically illustrating the conventional structure of a personal digital assistant with a battery unit mounted onto the housing. As shown in FIG. 1, the personal digital assistant 100 includes a housing 102, a battery unit 104, and a touch display panel 110. The housing 102 has a front cover 106a and a back cover 106b. The front cover 106a and the back cover 106b are affixed together with screws 108a and 108b. The front cover 106a and the back cover 106b must be designed to have a number of affixing holes with respect to the screws 108a and 108b, so as to allow the screws 108a and 108b to securely screw the front and back covers 106a, 106b together. In addition, the touch display panel 110 is implemented on the front cover 106a, so that a screen can be displayed to the user and the user can operate it by touching the panel. Because the extra battery unit 104 will be firmly mounted onto the back cover 106b of the housing 102, the manufacturer usually will design two transpiercing holes 112a and 112b in the extra battery unit 104. Also, the back cover 106b is designed to have two other affixing holes 114a and 114b. After the user inserts the screws 116a and 116b into the two transpiercing holes 112a and 112b, respectively, the user can firmly tighten the screws 116a and 116b into the affixing holes 114a and 114b by using a screwdriver. As a result, the extra battery unit 104 is affixed onto the back cover 106b. It is certain that the extra battery unit 104 must be coupled with the internal circuit board of the personal digital assistant 100, in order to supply the electric power for the prolonged use period.
It should be noted that the current trend of the PDA design is toward a light weight and compact product, so as to satisfy the practical need of the modern people. Thus, the size of the housing of the personal digital assistant needs to be reduced. Additionally, since the original front cover and the back cover have been affixed to the housing by a number of screws, it is not easy for the user to find the proper place to form the extra affixing holes on the more compact housing. This would make it difficult for the user to affix the extra battery unit onto the housing of the smaller personal digital assistant by using extra screws. Finally, the affixing holes 114a, 114b are located beside the screws 108a, 108b, and extend in the back cover 106b a distance through the internal circuit board received in the back cover 106b. This results in that valuable area of the internal circuit board is reduced, which increases the difficulty in layout of circuitry of the internal circuit board, particularly when the internal circuit board is used in the personal digital assistant, which is very small.